1. Field of the Invention
This invention relates to ionic polymers. More particularly, this invention relates to ammonium salts of anionic polymers, i.e. polymers containing covalently bound negatively charged groups. Most particularly, this invention is concerned with novel compositions of matter comprising certain higher alkyl ammonium salts or quaternary polyammonium salts of polymers having incorporated therein one or more covalently bonded anionic radicals selected from the group comprising sulfonate, carboxylate and phosphonate radicals.
The particular ammonium salts of this invention may be schematically represented as: EQU [C--A.sup.- ].sub.p+1 R.sub.3 N.sup.+ --[Q--R.sub.2 N.sup.+ ].sub.p R 1.
wherein C is one of a plurality of carbon atoms comprising a portion of the polymer backbone chain of carbon atoms or is in an acyclic, alicyclic or aromatic radical which is pendant to the backbone chain and wherein the C is in a single polymer molecule; A.sup.- is an anionic radical, preferably a sulfonate group, covalently bonded to one or more of the C carbon atoms; and wherein the R groups represent substituents of the nitrogen atom(s) which are each independently selected from the group comprising hydrogen or C.sub.1 to C.sub.50 straight and branched chain acyclic, alicyclic, aryl, alkylaryl, and arylalkyl radicals and substituted functional derivatives thereof, wherein at least one of the R groups is selected from the group comprising C.sub.12 to C.sub.50 straight and branched chain acyclic, alicyclic, aryl, alkylaryl, and arylalkyl radicals and substituted functional derivatives thereof, and wherein each Q is independently selected from the group comprising C.sub.1 to C.sub.40 divalent straight and branched chain alkylene cycloalkylene, arylene, dialkylene-arylene radicals and substituted functional derivatives thereof and --(CHY).sub.n --Z.sub.m --(CHY).sub.n, wherein Z is a hetero atom selected from the group consisting of oxygen and sulfur, m is zero or one, Y is hydrogen or said C.sub.1 to C.sub.50 radicals or substituted functional derivatives of the radicals and n is an integer of from 1 to 10, wherein p is from zero (for a monoammonium counterion) to about 10, more preferably zero to about 4, and most preferably zero or one, and wherein the ammonium counterion at least partially neutralizes said anionic acid radicals.
Other sulfonated salts of the instant invention are represented by the formula: EQU [C--SO.sub.3.sup.- ].sub.p+1 R'.sub.3 N.sup.+ --Q--R'.sub.2 N.sup.+ ].sub.p R' 2.
wherein C is one of a plurality of carbon atoms comprising a portion of the polymeric backbone chain of carbon atoms or is in an acyclic, alicyclic or aromatic radical which is pendant to the backbone chain and wherein the C is in a single polymer chain, the --SO.sub.3.sup.- groups are covalently bonded to one or more of the C carbon atoms in one or more of the polymeric backbone chains wherein each Q is independently selected from the group comprising C.sub.1 to C.sub.40 divalent straight and branched chain alkylene cycloalkylene, arylene, dialkylene-arylene radicals and substituted functional derivatives thereof and --(CHY).sub.n --Z.sub.m --(CHY).sub.n, wherein Z is a hetero atom selected from the group consisting of oxygen and sulfur, m is zero or one, Y is hydrogen or said C.sub.1 to C.sub.50 radicals or substituted functional derivatives of the radicals and n is an integer of from 1 to 10, wherein p is from one (for a diammonium counterion) to about 10, more preferably one to about 4, and most preferably one, and wherein the R' groups are each independently selected from the group comprising C.sub.1 to C.sub.11, preferably C.sub.1 to C.sub.4, most preferably C.sub.1 straight and branched chain acyclic, alicyclic, aryl, alkylaryl and arylalkyl radicals and substituted functional derivatives thereof.
For example, in formulas (3) and (4) below, diammonium and triammonium salts of formula 2 (p equal to 1 and 2 in formula (2)) are schematically represented as: ##STR1## where the symbols have the same meanings as in formula 2.
Using sulfonated polymers as the most preferred example of the anionic polymers of this invention, the ionically cross-linked ionomers of this invention may be readily prepared from the sulfonate precursor, for example a free sulfonic acid, by direct neutralization, either in bulk or in solution with an alkyl ammonium hydroxide wherein the cation is selected from one of the specified classes, or by a primary, secondary or tertiary amine from one of the specified classes, or by a combination of these neutralizing agents. Another means of preparation is by double decomposition (metathesis) of a salt of the sulfonic acid with an alkyl ammonium salt of an acid which is weaker (i.e. has a lower/pK.sub.a) than the sulfonic acid, or by double decomposition in a multiphase fluid medium in which the salt of the displaced counterion is selectively removed from the phase containing the polymer to a phse in which the ammonium ionomer is substantially insoluble.
The properties and utility of the ionic salts of this invention vary over a wide range depending on the structure of the anionic polymer, the average molecular weight and molecular weight distribution, the degree of neutralization of the anionic groups in the polymer, the mole concentration of the alkyl ammonium salt groups in the polymer, and in particular, the type and variety of the substituents attached to the nitrogen. The ionic salts can range from water-soluble polyelectrolytes useful as adhesives and thickening agents to elastomers or hard resins which are thermoplastic at elevated temperatures permitting the products to be extruded, injection molded, vacuum formed and sheeted.
A particularly useful form for an ionomer is a water-insoluble elastomer which can be melt fabricated and then used without curing, and which can subsequently be reprocessed at elevated temperature since the ionomer does not contain permanent crosslinks.
2. Description of the Prior Art
Polymers containing anionic groups and their metal salts, prepared either by covalently appending anionic groups to a preformed polymer, as for example, by sulfonation or grafting of anionic monomers, or prepared by the mono or interpolymerization of monomers having acid moieties are old in the art.
U.S. Pat. No. 3,642,728 discloses sulfonated elastomer polymers which can be neutralized with organic amines having C.sub.1 to C.sub.30 carbon atoms. This broad disclosure of organic amines encompasses systems which fail to provide sulfonated elastomeric systems which are capable of being readily extruded into high performance elastomeric articles and which are limited to slower and less economical processes such as compression molding. The sulfonated polymers neutralized with the higher alkyl ammonium substances which are represented in formula (1) of the instant invention quite unexpectedly exhibit substantially improved melt flow at processing temperatures thereby enabling the instant polymers to be readily processed through an extruder into high performance polymeric articles.
In contrast to the higher alkyl substituted sulfonated polymers represented by formula (1) of the instant invention, the quaternary di- and polyammonium neutralized sulfonated polymers represented in formula (2) of the instant invention tend to possess high tensile strengths, especially at elevated temperatures. These materials have particularly outstanding high temperature tensile properties when Q is a straight chain alkylene radical which contains from 4 to 30 carbon atoms, preferably 4 to 22 carbon atoms and most preferably 6 to 18 carbon atoms.
U.S. Pat. No. 3,836,511 discloses sulfonated elastomer polymers which are neutralized with lower alkyl amines. These amine-neutralized, sulfonated elastomers do not possess the improved melt processability and greater softness of the higher alkyl ammonium-neutralized, sulfonated elastomer of the instant invention.
Reference is also made to copending application U.S. Ser. No. 855,553, now U.S. Pat. No. 4,137,203, issued Jan. 30, 1979, which contains a comprehensive prior art survey on ionomers.